Problem: A group of adults and kids went to see a movie. Tickets cost $$8.50$ each for adults and $$4.50$ each for kids, and the group paid $$48.50$ in total. There were $5$ fewer adults than kids in the group. Find the number of adults and kids in the group.
Let $x$ equal the number of adults and $y$ equal the number of kids. The system of equations is then: ${8.5x+4.5y = 48.5}$ ${x = y-5}$ Solve for $x$ and $y$ using substitution. Since $x$ has already been solved for, substitute ${y-5}$ for $x$ in the first equation. ${8.5}{(y-5)}{+ 4.5y = 48.5}$ Simplify and solve for $y$ $ 8.5y-42.5 + 4.5y = 48.5 $ $ 13y-42.5 = 48.5 $ $ 13y = 91 $ $ y = \dfrac{91}{13} $ ${y = 7}$ Now that you know ${y = 7}$ , plug it back into ${x = y-5}$ to find $x$ ${x = }{(7)}{ - 5}$ ${x = 2}$ You can also plug ${y = 7}$ into ${8.5x+4.5y = 48.5}$ and get the same answer for $x$ ${8.5x + 4.5}{(7)}{= 48.5}$ ${x = 2}$ There were $2$ adults and $7$ kids.